Size Effects in Coexistence Conditions

Performed Monte Carlo simulations [178,179] confirm the conclusion, that surface segregation of the minority component plays an important role in the suppression of the phase diagram. The segregation occurs on a scale of the correlation length for any film with varied thickness D, but only for small D ( 4 [178]) it leads to visible divergence of the average compositions (] and (t 2 from their bulk (binodal) values ((h and ( 2. 

The picture presented above is not complete as it neglects non-mean field behavior of polymer blends in the temperature range close to Tc [149]. The Ising model predicts phase diagrams of thin films, which are more depressed and more flattened than those yielded by mean field approach (as marked in Fig. 31d). Both effects were shown by Monte Carlo simulations performed by Rouault et al. [150]. In principle, critical regions of phase diagrams cannot be described merely by a cross-over from a three- to two-dimensional (for very thin films) situation. In addition, a cross-over from mean field to Ising behavior should also be considered [6,150]. 

Detailed (mean field) analytical calculations were performed by Tang et al. [219] to evaluate the shift in the critical temperature TCD of a thin film as a function of D. They considered a symmetric polymer blend confined by neutral 

Very recent Monte Carlo simulations and self consistent mean field calculations [223] have shown that wetting properties might be reflected in the phase diagram of a blend confined between symmetric selective surfaces Close to Tw a convex curvature is exhibited by the phase diagram on the side poor in preferentially adsorbed polymer. Also the temperature dependence of Ap changes around the wetting point Tsv. 

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